The carcinogenic potential of benzidine and other aromatic amines has been recognized for many years. Most data has measured risks in workers exposed to the manufacture of beta-naphthylamine as well as to benzidine and other chemicals. Employees of a local chemical plant have had exposure primarily to benzidine. A study of these employees may add to our present knowledge of the risks of this exposure. How frequent are cancers of the bladder and urinary tract in this population? Do the wives of workers from cohorts of early employees have an excess risk of cancer due to possible exposure to contaminated clothing? Are there any indications that benzidine might produce changes in the offspring of workers and spouses? To answer some of these questions, we will locate current and former employees of the plant, examine them, and determine the prevalence of cancer by history and current physical status. The data will be analyzed by cohorts of employment and by estimated dose and duration of exposure to benzidine. Cancer rates will be compared by gradation of exposure, time of exposure, and comparable U.S. city rates.